In the above-mentioned technical field, a handover is attempted when the quality of wireless communications deteriorates, but a control signal for issuing a handover instruction to a mobile communications terminal (UE: User Equipment) has a large data size and is therefore less likely to be delivered to the UE upon the deterioration in quality of wireless communications. When the control signal cannot be delivered to the UE and a handover results in failure, RRC Connection reestablishment is attempted upon detection of RLF (Radio Link Failure) on the UE side. When this attempt also results in failure, the UE makes a transition to the RRC_IDLE state. At the time of failure of a handover, since only information sent by a system information block (System Information Block) is used as information for a cell search, no appropriate cell can be immediately selected, so the “out of service range” state may continue.
PTL 1 discloses a technique for, if the channel shows deterioration when packet data is redirected upon failure of HARQ (hybrid automatic redirection request) from a transmitter to a receiver, re-fragmenting data of an RLC-SDU (Radio Link Control Service Data Unit) or an RLC-PDU (Radio Link Control Protocol Data Unit) into PDU data having a smaller size, and sending the re-fragmented RLC-PDU data.